ISO 8601 is a long document which none of us can read and which specifies A LOT of different formats, including 2023-10-21, +0020231021, 2023-W42, 2023-294, and a lot of others (including duration specifiers).

Citing RFC 3339 is usually a better idea, since in addition to be readable for free, it is limited to the date formats you are thinking about. My 2 cents on your preferred citation, keep preaching though!

https://datatracker.ietf.org/doc/html/rfc3339

With apologies for the delayed response, I got here from the weekly hackernewsletter.